The present invention pertains to spectrographic and reflectance data analysis and more particularly to screening and identifying materials, such as pharmaceutical or food products, being packaged in an automated machine.
Optical spectrometers allow the study of a large variety of samples over a wide range of wavelengths. Materials can be studied in the solid, liquid, or gas phase either in a pure form or in mixtures. Various designs allow the study of spectra as a function of temperature, pressure, and external magnetic fields.
Near-Infrared (NIR) spectroscopy is one of the most rapidly growing methodologies in product analysis and quality control. In particular, NIR is being increasingly used as an inspection method during the packaging process of pharmaceuticals or food products. More and more often, this technique is augmenting or even replacing previously used vision inspection systems. For example, an NIR inspection system can be used to inspect a pharmaceutical blister package (such as an oral contraceptive or allergy medication) for, among other things, physical aberrations, chemical composition, moisture content, and proper package arrangement.
Most notably, NIR spectrometry inspection systems can be used to evaluate the chemical composition of products during the packaging process. Particularly with solid dosage pharmaceutical products, a group or package of products may look identical in the visible portion of the spectrum but may have unique chemical signatures in the near-infrared range (e.g. the 800-2500 nm range). Variations in the chemical composition of a tablet or capsule are usually grounds for rejecting a package containing a tablet with such a discrepancy. In operation on a pharmaceutical blister packaging machine, a still uncovered blister pack containing tablets or capsules passes an inspection station where it is examined. Once the inspection device inspects the blister pack to ensure that the correct material is located in each of the tablet or capsule wells, the packaging machine seals the blister pack. Those packages that fail the inspection process are rejected at a subsequent station. Subject to regulatory requirements, the rejected tablets may also be recycled for further processing.
The use of vision systems as an inspection mechanism continues to become less desirable as the need for more in depth inspection procedures and near 100% inspection processes are desired. Of particular concern is that known vision systems are inherently incapable of performing a chemical analysis of the product being packaged. Rather, vision systems rely solely on a comparison of a visual snapshot of the package to a previously stored reference image. Known vision packaging inspection systems xe2x80x9clookxe2x80x9d at each individual package to see whether it has the correct number of doses in the pack. For example, vision systems look for missing or overfilled tablet wells. In some cases, physical discrepancies, cracks, or gouges on a tablet will also cause a vision system to reject the package. What may not be detected by a vision system is the situation where each of the products in a package appears to be similar and in conformance with a reference image but the formulation of one or more products within the package are incorrect, or the wrong product composition is inserted into the packaging. The limitations of these types of known visions systems become readily apparent when higher levels of inspection are required and when they are compared with the expanded capabilities of a spectrometer-based inspection system.
In order to calibrate known spectrometer inspection systems, it is necessary to normalize the spectrometer to a stable reference sample. Typically, a material having a near 100% reflectance is selected for the reference material. The raw spectrum of this reference sample is measured by the spectrometer in order to provide a reference for normalizing subsequent measurements. This is done by dividing the measured raw spectrum of target samples by the previously measured raw spectrum of the reference sample. The normalized spectrum of the target sample is then used in conjunction with the previously established baseline to evaluate whether a discrepancy exists in the samples actually subjected to examination or inspection.
This method, however, requires that the packaging or inspection system be loaded with a stable reference sample, typically one with near 100% reflectance at the beginning of each packaging run in addition to providing known samples for comparison purposes. The addition of another step to the inspection process introduces other sources of error into the system and adds to the overall inspection time and cost.
It is therefore desirable to have a spectrometer-based inspection system that does not require a stable reference sample to be loaded into the packaging equipment in addition to a calibration set. It is also desirable to have a spectrometer-based inspection system that minimizes the number of steps required to obtain a relative spectrographic measurement of a package of items and that allows for calibrations specific to particular material properties applicable to a range of material compositions.
In one aspect, a method of calibrating a spectrographic inspection system, comprises providing a plurality of packages, each of the plurality of packages containing a group of items, wherein each of the groups of items has a known composition, measuring the reflectance value of each of the groups of items and thereby obtaining a reference reflectance value set, normalizing the reference reflectance value set and thereby creating a normalized reference reflectance value set, and storing the normalized reference reflectance value set.
In another aspect, a method of analyzing a package of items comprises providing a first package containing a first group of items, wherein the first group of items has a known composition, measuring the reflectance value of the first group of items, thereby obtaining a reference reflectance value, normalizing the reference reflectance value and thereby creating a normalized reference reflectance value, storing the normalized reference reflectance value, providing a second package containing a second group of items, wherein the second group of items has an unknown composition, measuring the reflectance value of the second group of items to obtain a target reflectance value, normalizing the target reflectance value and thereby creating a normalized target reflectance value, comparing the normalized target reflectance value with the normalized reference reflectance value, and determining whether the normalized target reflectance value conforms with the normalized reference reflectance value.
In a further aspect An inspection system, comprises an inspection station adapted to obtain reflectance data corresponding to a first package and adapted to gather reflectance data corresponding to a second package, and a processor communicatively coupled with the inspection station and adapted to normalize the reflectance data obtained by the inspection station, thereby creating normalized reflectance data, wherein the processor is further adapted to compare the reflectance data corresponding to the first package with the normalized reflectance data corresponding to the second package.
As will become apparent to those skilled in the art, numerous other embodiments and aspects will become evident hereinafter from the following descriptions and claims.